The main objective of this proposal is to develop an in vitro predictive system to evaluate the response of human tumors to a broad spectrum of chemotherapeutic agents before a patient is scheduled to a particular therapeutic regimen by making use of the phenomenon of premature chromosome condensation. This approach is based on the fact that most of the cancer chemotherapeutic agents not only cause cell death but also induce chromosome aberrations. In the literature there is ample evidence to support the existence of a positive correlation between chromosomal damage and cell death. The PCC method makes it possible to visualize chromosome damage in interphase cells or in those cells that will not be able to enter mitosis because of the lethal effects of the treatment. Cells from human tumors treated in vivo or in vitro with a given drug will be fused with mitotic HeLa cells and the prematurely condensed chromosomes (PCC) of the tumor cells will be scored for aberrations. Agents that produce the highest incidence of aberrations are expected to be effective against that particular tumor. The data on chromosome aberrations and the clinical regression of the tumor will be compared to find any correlations. If this method shall prove to be effective, it will eliminate the present empirical clinical trials and save the patients from undergoing therapeutic regimens that are useless to them.